/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package spark.stream;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.regex.Pattern;

import scala.Tuple2;
import kafka.serializer.StringDecoder;

import org.apache.spark.SparkConf;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.PairFunction;
import org.apache.spark.streaming.api.java.*;
import org.apache.spark.streaming.kafka.KafkaUtils;
import org.apache.spark.streaming.Durations;

/**
 * Consumes messages from one or more topics in Kafka and does wordcount.
 * Usage: JavaDirectKafkaWordCount <brokers> <topics>
 * <brokers> is a list of one or more Kafka brokers
 * <topics> is a list of one or more kafka topics to consume from
 * <p>
 * Example:
 * $ bin/run-example streaming.JavaDirectKafkaWordCount broker1-host:port,broker2-host:port \
 * topic1,topic2
 */

public final class JavaDirectKafkaWordCount {
    private static final Pattern SPACE = Pattern.compile(" ");

    public static void main(String[] args) throws Exception {
        if (args.length < 2) {
            System.err.println("Usage: JavaDirectKafkaWordCount <brokers> <topics>\n" + "  <brokers> is a list of one or more Kafka brokers\n"
                    + "  <topics> is a list of one or more kafka topics to consume from\n\n");
            System.exit(1);
        }

        String brokers = args[0];
        String topics = args[1];

        // Create context with a 2 seconds batch interval
        SparkConf sparkConf = new SparkConf().setAppName("JavaDirectKafkaWordCount");
        JavaStreamingContext jssc = new JavaStreamingContext(sparkConf, Durations.seconds(2));

        Set<String> topicsSet = new HashSet<>(Arrays.asList(topics.split(",")));
        Map<String, String> kafkaParams = new HashMap<>();
        kafkaParams.put("metadata.broker.list", brokers);

        // Create direct kafka stream with brokers and topics
        JavaPairInputDStream<String, String> messages = KafkaUtils.createDirectStream(jssc, String.class, String.class, StringDecoder.class, StringDecoder.class, kafkaParams, topicsSet);

        // Get the lines, split them into words, count the words and print
        JavaDStream<String> lines = messages.map(new Function<Tuple2<String, String>, String>() {
            @Override
            public String call(Tuple2<String, String> arg0) throws Exception {
                return arg0._2;
            }
        });
        JavaDStream<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
            @Override
            public Iterator<String> call(String arg0) throws Exception {
                return Arrays.asList(SPACE.split(arg0)).iterator();
            }
        });
        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(new PairFunction<String, String, Integer>() {
            @Override
            public Tuple2<String, Integer> call(String arg0) throws Exception {
                return new Tuple2<String, Integer>(arg0, 1);
            }
        }).reduceByKey(new Function2<Integer, Integer, Integer>() {
            @Override
            public Integer call(Integer arg0, Integer arg1) throws Exception {
                return arg0 + arg1;
            }
        });
        wordCounts.print();

        // Start the computation
        jssc.start();
        jssc.awaitTermination();
    }
}
